Effectiveness of greenhouse gas mitigation intervention for health-care systems: a systematic review

Abstract Objective To identify evidence-based interventions that reduce greenhouse gas emissions in health-care systems in low- and middle-income countries and explore potential synergies from these interventions that aid climate change adaptation while mitigating emissions. Methods We systematically searched 11 electronic databases for articles published between 1990 and March 2023. We assessed risk of bias in each article and graded the quality of evidence across interventions in health-care operations, energy and supply chains. Findings After screening 25 570 unique records, we included 22 studies published between 2000 and 2022 from 11 countries across six World Health Organization regions. Identified articles reported on interventions spanning six different sources of emissions, namely energy, waste, heating and cooling, operations and logistics, building design and anaesthetic gases; all of which demonstrated potential for significant greenhouse gas emission reductions, cost savings and positive health impacts. The overall quality of evidence is low because of wide variation in greenhouse gas emissions measuring and reporting. Conclusion There are opportunities to reduce the greenhouse gas emissions from health-care systems in low- and middle-income countries, but gaps in evidence were identified across sources of emissions, such as the supply chain, as well as a lack of consideration of interactions with adaptation goals. As efforts to mitigate greenhouse gas intensify, rigorous monitoring, evaluation and reporting of these efforts are needed. Such actions will contribute to a strong evidence base that can inform policy-makers across contexts.


Introduction
In the absence of actions to rapidly reduce global greenhouse gas emissions, climate change is predicted to be the biggest threat to human health in the 21st century.Direct and indirect health effects from climate change include exposure to extreme weather, undernutrition, the spread of vector-borne diseases, lack of access to clean water, and mental health effects. 1 Health-care systems are facing the challenge of treating these impacts, but they also emit about 4.4% of global greenhouse gas emissions with projected increases in emissions. 2,3Since the United Nations Framework Convention on Climate Change 26th Conference of Parties in 2021 (UNFCCC COP26), 75(54 low-and middle-income) countries have committed to transitioning to sustainable, low-carbon health systems, with 29 (22 low-and middle-income) countries aiming to reach net-zero emissions in their health-care systems. 4,5ealth-care systems in low-and middle-income countries emit lower per capita greenhouse gas emissions compared to those in high-income countries, 2,3 but as healthcare systems in many low-and middle-income countries advance, an increase in emissions is likely unless steps are taken to identify, measure and control them.Low-and middle-income countries are also predicted to experience the harmful effects of climate change with greater intensity and at an earlier stage due to their geographical location, exposure and vulnerability, while being less equipped to handle these effects due to a shortage of resources to cope and recover. 6,7Any adaptation actions undertaken by health-care systems should not exacerbate the health sec-tor's greenhouse gas emissions, creating negative feedback loops and locking them into higher emission trajectories.
To fulfil the commitments undertaken at, and since, COP26, it is necessary to identify evidence-based strategies for reducing the greenhouse gas emissions of healthcare systems in low-and middle-income countries. 8We undertook a systematic review to identify modelled and implemented greenhouse gas mitigation interventions and their relationship with adaptation, applicable within the context of low-and middle-income countries, to provide evidence on which interventions are most feasible to implement and where actions can be scaled to provide significant reductions in emissions within health-care facilities and across the sector.

Methods
We followed a protocol published on 4 August 2022 9 following the Preferred reporting items for systematic review and meta-analysis protocols 10 checklist (online repository). 11The protocol underwent one methodological amendment, namely the removal of the Joanna Briggs Institute Critical Appraisal Tools for evaluation, as they were not relevant to the types of interventions we analysed. 12We searched the database Ovid MEDLINE®, Ovid Embase®, Global Health, Web of Science, Africa-Wide Information, LILACS, Global Index Medicus, ELDIS, SCO-PUS, AfricaPortal and GreenFILE on 17 March 2023.We predetermined the inclusion and exclusion criteria, which are detailed in Box 1.

Search strategy
Our search strategy consisted of three main elements: (i) the health-care system; (ii) greenhouse gases; and (iii) low-and middle-income countries (Box 2 and online repository). 9,15o further structure our strategy, we devised a conceptual theory of change framework.We used approaches outlined by the United Nations Sustainable Development Group Latin America and the Caribbean and the New Philanthropy Capital and insights from a previous publication to develop this framework. 16,17The framework is defined in (Box 3; available at: https:// www .who.int/publications/ journals/ bulletin/ ) and detailed descriptions of each section can be found in our online repository. 15

Selection process and data extraction
We uploaded records using Rayyan QCRI software (Rayyan, Cambridge, United States of America), and the aforementioned inclusion and exclusion criteria were applied throughout the screening process.Following published efficiency guidelines, 18 we removed duplicates, screened titles and analysed abstracts and full texts against eligibility criteria using Rayyan QCRI.Two reviewers performed each step separately, after which any disagreements were discussed.If no consensus was reached, a third author was consulted for resolution.Two reviewers independently extracted all relevant data from eligible articles using a pre-tested form with detailed instructions (Box 4).This extracted data was used to generate a 100-word or less summary on the extraction sheet.
We assessed risk of bias using specifically designed questions intended to be applicable across different study types using a simple judgement of low risk, high risk or unclear risk on different axes as endorsed by the Cochrane Collaboration. 42Independent assessments were made by at least two authors.
We assessed the overall strength of evidence resulting from article synthesis using the Grading of recommendations assessment, development, and evaluation (GRADE) approach.The collated evidence was graded using four different categories: (i) very low (we believe the true effect is probably very different from the estimated effect); (ii) low (we believe the true effect might be very different from the estimated effect); (iii) moderate (we believe that the true effect is probably close to the estimated effect); or (iv) high (we are confident that the true effect is similar to the estimated effect). 43We used GRADEpro Guideline Development Tool (McMaster University and Evidence Prime, Hamilton, Canada) for the analysis.

Results
Our search yielded 25 570 records.After removing duplicates and screening the titles, abstracts and full texts, 22 articles met the inclusion criteria (Fig. 1).

Publication types
Peer-reviewed primary research including analytical cross-sectional studies, case-control studies, case reports, cohort studies, diagnostic test accuracy studies, and randomized controlled trials.We excluded other types of publications, such as protocols, guidelines, (systematic) reviews, perspectives, commentaries or editorials.We screened relevant reviews for primary research references.

Languages
No restriction.

Context
Findings of research in one or more low-and middle-income countries.

Topic
Any implemented or modelled greenhouse gas mitigation intervention across health-care operations, energy and supply chains.

Outcome
Reporting a quantified change in greenhouse gas emissions from the intervention.

Timeline
Published between 1990 and 17 March 2023.Study settings vary from regional systems to urban areas, hospitals and rural centres (Table 1).

Interventions
Of the selected articles, we identified six primary intervention areas: energy (10 studies); waste (eight studies); heating and cooling (one study); operations and logistics (one study);building design (one study); and anaesthetic gases (one study).All articles detailed implementation; 14 discussed costs; 13 reported health effects; and one considered adaptation to the effects of climate change.
Twenty articles included data on carbon dioxide reduction whereas only two articles reported on other greenhouse gases or pollutants (Table 2).For one article, we could only extract percent reduction of emissions 20 and for five others no percentage could be calculated as original emissions were not provided. 21,26,31,33,40hree articles 24,38,40 only reported decreases in electricity usage, which was converted to carbon dioxide equivalent using the national grid emission factor. 45,46Two articles 24,27 included a 100% reduction of carbon dioxide emissions and in this case the supply chain, installation of the system and relevant upkeep were not considered.Three articles indicated more than 100% reduction due to zero-emission electricity generation and selling the surplus. 28,32,38The intervention areas of energy and waste are outlined below, and the other four areas are described in Box 5.

Energy interventions
We identified reports on hybrid energy systems using a combination of non-renewable and renewable energy sources [20][21][22]25,26,28,29 or fully renewable sources; 23,24,27 achieving carbon dioxide emission reductions of 25%-233% as compared to alternative scenarios (Table 2) where the reductions higher than 100% are attributed to surplus electricity generation exported to the grid. All repored energy systems featured solar photovoltaic electricity generation paired with various other sources, such as wind or diesel.Greenhouse gas emissions from production and installation were generally not considered, and no unintended consequences were reported. One artile compared legal contexts and concluded that flexibility to sell or export electricity to the grid maximizes annual carbon dioxide emission savings.28

Implementation
We found that all study authors recognized hybrid energy systems as acceptable interventions when consid-ering various factors such as electricity generation, environmental impact and economic feasibility.25]28 Scalability could extend to commercial buildings and agricultural industries as well. 21,27nitial capital costs and access to sufficient finance may act as a barrier to implementation of hybrid energy systems, but hybrid energy systems Types of research methods used in the article

Geographical scale:
Whether the study was conducted at a local, regional, national or international level

Location:
Relevant town or city, region, country and/or countries where the research was conducted

Part of the health-care system:
A particular aspect of the health-care system such as a primary health-care facility or a rural hospital

Greenhouse gas mitigation intervention(s):
Intervention details that lead to a decrease in greenhouse gas emissions

Measurable effects of the greenhouse gas mitigation intervention(s):
Quantified effects of the identified intervention(s) on mitigation, including a specification of greenhouse gas or carbon dioxide equivalent and whether it was measured or modelled

Implementation process:
A description of the implementation process, including enablers and barriers and how these were approached

Implementation timeline:
Timeline of the implementation process

Economic analysis:
Any provided economic information such as cost-effectiveness, cost-benefit or cost consequences

Linkage with adaptation or resilience:
Whether the intervention was directed at both mitigation and adaptation or if resilience was described.These interactions can be synergies, co-benefits, conflicts, trade-offs or co-harms 19

Health effects:
Measured effects on health outcomes or exposures

Funding source:
Source of funding for the authors

Conflicts of interest:
Further

Research
were seen as a solution to enhance energy reliability and reduce energy costs over time. 232][23] Wind and solar potential significantly influences their implementation, as areas with high potential (for example, those with strong insolation for solar energy), are more conducive to successful deployment than low-potential areas.

Economic analysis
Eight articles reported details on costing, including their Net Present Costs (ranging from 3658 to 146 284 United States dollars, US$), payback periods (ranging from 3.38 to 9.9 years), and return metrics, which vary across different systems and locations (Table 3).

Health and health equity
Five articles qualitatively estimated potential health effects, noting that reliable hybrid energy systems can prevent power interruptions and address the lack of access to reliable electricity in rural areas.Without continuous access to electricity, the lack of essential medical equipment -such as incubators, ventilators and basic lighting, critical for safe childbirth and neonatal care -leads to a high rate of maternal and perinatal mortality; spoilage of medication; and the inability to sterilize medical equipment used in operating rooms.In addition to the negative effects noted above, lack of coordination and communication (hindered by lack of reliable access to electricity or broadband wireless networks) was also found to disproportionately affect the health care of women and children.][25] Other important actions such as replacing diesel generators with hybrid systems can act to reduce harmful exposure to pollutants including unburned hydrocarbons and particulate matter; potentially reducing risks for lung cancer, asthma and bronchitis; 29 as well as contributing to a safer work environment particularly in laboratory settings. 24

Adaptation
Authors of one study examined the intersection of mitigation and adaptation in the context of a solar photovoltaic energy system with and without grid-connection for a rural health-care facility in the Philippines.They defined a climate-resilient energy system as providing "reliable, safe, and secure electricity during short-term disasters and events and as longer-term climate changes occur", and found that this solar photovoltaic energy system could enable continued provision of care during both short-and longer-term climate change effects. 23,47

Waste interventions
Of the eight studies on waste that we identified, one study covered plasma melting; used for melting medical waste.Plasma melting appears to have the highest overall relative greenhouse gas emissions as compared to alternative waste interventions. 372]37 Relative emission reductions can be achieved by centralizing the autoclave, ensuring efficient transportation and having well-trained operators. 31,36One article also considered water usage, and found that combining autoclaving with incineration may conserve 38 967 m 3 of water annually compared to incineration alone (Table 2). 31][34] Any further reductions in emissions were achieved through material recovery. 32For example, cardboard sharps containers were found to reduce black carbon emissions by 62% compared to plastic sharps containers in an incineration-only system. 35eported methodological limitations around waste management data include: (i) neglecting heat recovery; 30,37 (ii) lack of accurate waste data; 32 (iii) inability to measure electricity during operations and autoclaving; 33 (iv) foreign emission factors; 33 and (v) omission of transportation. 34,37Unintended negative consequences of waste management include ineffective segregation leading to exposure to hazardous items, 30 and generation of toxic dioxin during recycling. 34

Fig. 1. Flowchart of the selection of studies on greenhouse gas mitigation interventions
for health-care systems

Implementation
Appropriate waste management also acts to improve health and safety while reducing greenhouse gas emissions. 32hree articles recommended scaling up the proposed waste management systems within their respective cities and regions, [30][31][32] one more broadly across low-and middle-income countries, 31 while another recommended a global ban on plastic sharps containers. 35For example, composting of biodegradable waste in Pakistan was easy to implement because of low management and operation costs. 32n Türkiye, incineration on its own was not feasible due to high costs. 31ltimately, widespread segregation and material and energy recovery was recommended but funding may be a barrier to implementation. 32actors contributing to successful interventions include introduction of new technology (such as a wellperforming scrubber control system), capacity-building and carbon tax policies. 32,34,36Barriers to successful implementation include unskilled operators, ineffective segregation and illegal removal of waste for recycling.Several policy interventions were suggested by the authors to deal with these potential barriers. 30,34,36

Economic analysis
In a study from China, authors estimated that appropriate plastic recycling in the health-care system would lead to a cumulative economic benefit of about US$ 450 million in 2050. 34In another article, a cost-benefit analysis indicates that electricity generation from waste can cover a large portion of the fuel expenses of transportation and incineration of medical waste. 32

Health and health equity
Reducing black carbon and sulfur emissions from incineration can reduce health risks, such as respiratory infections, low birth weight, premature deaths and asthma, in localities where incineration is happening nearby. 35,36lthough waste burning is a relatively small contributor to black carbon globally, it is a substantial contributor to health-related illnesses in locations with high black carbon exposure such as in China, India, Nigeria and Republic of Korea. 48

Critical appraisal and risk of bias
Definitions of relevant methodological terms in the included studies were generally clear, but details on methods were missing in nine out of 22 (41%) articles.Fourteen studies (64%) reported on modelled outcomes, and eight (36%) reported on empirical outcomes.Some outcomes lacked transparency (missing data, time frames or units; six studies, 27%) and/or lack of confounding (eight studies, 36%).Seven articles (32%) did not clearly state assumptions, and 14 (64%) did not clearly state limitations.We did not note a conflict of interest partly because 12 articles (55%) did not include a conflict-of-interest statement.Funding sources included health ministry funds, government funds, national foundations and institutes, university grants, corporations, 23 research councils and national programmes (Table 4).
As no protocols were published in advance, we could not compare and identify selective reporting for any of the articles.None of the articles selfreported potential meta-biases.

Confidence in cumulative evidence
We evaluated confidence in the available evidence regarding the effect size of greenhouse gas emission reductions using the GRADE certainty assessment (Table 5), which is described in detail in the online repository. 15Across all 10 articles on energy, outcomes were assessed, as they spanned a variety of hybrid energy systems that included renewable energy resources.Regarding waste, we assessed four separate outcomes based on the different interventions described in the articles.The four remaining articles were assessed as separate outcomes in the text.

Discussion
Here we provide an overview of peerreviewed evidence on greenhouse gas mitigation interventions for health-care systems in low-and middle-income countries.The eligible studies show reductions in greenhouse gas emissions, cost savings as well as potential positive health effects.Because the overall health sectoral emissions contribute to about 5% of global greenhouse gas emission, successful mitigation efforts need to be urgently scaled up to affect overall emissions.For example, in 2015, Chinese health-care systems emitted an estimated 302 megatonnes (Mt) of carbon dioxide, while the Kenyan and Malaysian systems emitted an estimated 2 Mt and 6 Mt of carbon dioxide, respectively. 2n our identified studies, the maximum reductions were approximately 0.9 Mt of carbon dioxide equivalent annually for a sustainable waste approach in China; and 0.02 Mt of carbon dioxide equivalent for a hybrid polygeneration energy system in a Brazilian hospital. 28,34owever, due to the limited identified records and inconsistent methods, the overall quality of evidence is low and supports the conclusion that rigorous research, publication and dissemination is needed.
Fully renewable energy with battery storage, or hybrid energy systems including renewable and conventional sources provide a reliable and sustainable source of electricity, especially in areas with intermittent or unreliable grid electricity supply; and require decision-makers interested in implementing renewable energy systems to consider local conditions, such as energy prices, solar and wind parameters, and temperature to optimize performance and sustainability.A primary barrier to implementation is the high initial cost to purchase, install and maintain such systems or interventions.Irrespective of these barriers, we identified seven articles that reported positive returns, suggesting that the long-term benefits of implementing renewable energy systems outweigh the initial costs of implementation.Adequate funding is therefore crucial to support the initial setup of these mitigation interventions.
Our results highlight actions such as waste segregation, composting and material recycling as means to reduce greenhouse gas emissions, which is consistent with evidence from other sectors and high-income country settings. 49,50Waste-to-energy technologies such as incineration, autoclaving and microwave sterilization could contribute more to greenhouse gas emission reductions than plasma melting or landfilling.We recommend that health-care facilities prioritize waste reduction, segregation and recycling, and address identified barriers through capacity-building and incentives before considering waste-to-energy technologies.9][40][41] Although we have reviewed several promising interventions to reduce greenhouse gas emissions in health-care settings, there are gaps in our current knowledge of the implementation and sustainability of mitigation interventions and their potential scalability.These gaps restrict our understanding of the effects on overall sectoral emission reductions.Detailed information is lacking on the workforce required, the amount of implementation-related greenhouse gas emissions, and the time and resources needed for installation and deployment.Moreover, there is little information on other important issues such as longterm maintenance and upkeep.
This study has some limitations.First, the findings may not encompass all pertinent factors leading to successful implementation because of a lack of descriptive details.Second, the absence of consistent reporting methods in the literature restricts the comparability and generalizability of the results and impedes further in-depth analysis.Third, the GRADE approach is designed for single interventions, which creates challenges in the interpretation of systemic change.To overcome these limitations, further research is necessary to obtain more comprehensive evidence on the effectiveness, scalability and durability of mitigation interventions in healthcare systems in low-and middle-income countries using standard approaches; for example by adapting guidelines for evaluation of complex interventions to the planetary health agenda. 51,52ountry, reference

Type of outcome measurement
Reduction CO We found that the types of interventions reported in the literature are limited to a few areas that contribute to emissions, namely energy, waste, heating and cooling, operations and logistics, building design and anaesthetic gases.We also noted a lack of reported interventions in other subject areas including equipment efficiency; inhalers; food; manufacturing and efficient use of pharmaceuticals and chemicals; production, reduction and circularity of medical supplies and devices; partnerships, purchasing and finance; information and communication technologies; telemedicine; community-based care; and supply-chain management. 8Further, interventions focusing on systemic efficiencies of delivery of high-quality care were not identified and improving the efficiency of health-care provision could provide another opportunity to reduce emissions (Box 3).
There is a lack of data on how to consider context-specific adaptation and mitigation measures, particularly in low-and middle-income countries.Future research and interventions should consider a wider range of contexts, including low-income countries, all scopes of emissions and adaptation.While efforts are increasing to mitigate greenhouse gas emissions from healthcare systems, such as through WHO's Alliance for Transformative Action on Climate Change and Health, 53 it is essential to robustly monitor, evaluate, record and report outcomes in a standardized manner.An example of a tool that could support such efforts is the recently launched HealthcareLCA database, which contains assessments focused on the environmental impact of health care. 54In addition, reviewing grey literature such as reports from nongovernmental organizations, local organizations and community-based initiatives could provide valuable insights into the implementation and sustainability of interventions in low-Box 5. Other greenhouse gas mitigation interventions in health-care systems

Heat exchanger system, Malaysia
A hospital ward in Malaysia incorporated an eight-row heat pipe heat exchanger into its air conditioning system, yielding savings equivalent to approximately 314 kg of carbon dioxide each year.This system also provides an economic benefit of about US$ 42 000 annually with a payback period of 1.6 years, and offers the added advantage of preventing Legionella growth in the ducting system. 38

Sevoflurane use, India
Using only the induction dose of sevoflurane for brief paediatric eye examinations in children aged 1-5 years reduced emissions in comparison to the traditional continuous low flow.Despite the high global warming potential of sevoflurane, this reduction in usage amounts to a modest climate benefit and cost savings of US$ 10 per day across 8-12 patients, enhancing health equity and affordability of this vital anaesthetic for children in low-resource settings. 39

Building design, China
A hospital's new outpatient lobby design in a colder region of China, featuring two south-facing exterior walls over a 16 m 2 area, is expected to achieve a significant reduction in carbon dioxide emissions, between 186 and 1011 kg annually, due to the decreased need for heating. 40

Multiuse pharmaceuticals and reusing surgical supplies, India
Cataract surgery at the Aravind Eye Care Centre in India, when compared with similar procedures in the United Kingdom of Great Britain and Northern Ireland, showed that implementing multiuse pharmaceuticals and reusing surgical supplies led to a substantial 95% relative reduction in emissions.The centre also optimized surgical duration and turnaround times, running two adjacent operating rooms simultaneously, which contributed to better patient outcomes and lower complication rates.Nonetheless, the assessment acknowledged methodological limitations, including variance in greenhouse gas measurement techniques and a lack of life cycle inventories specific to India.The researchers advocated for the expansion of such interventions, suggesting new vision centres and the integration of telemedicine, supported by rigorous training and strict sterilization protocols.They highlighted that policy changes, particularly those allowing multiuse pharmaceuticals in more countries, are essential to mitigate the environmental impact of health-care practices. 41$: United States dollars.

Box 4 .
Data extracted for each article identified in the systematic review on greenhouse gas mitigation interventions for health-care systemsArticle identifiers:Basic identifiers including name, authors, date, journal, article type and article design Methods:

search line and content of search parameters to identify articles on greenhouse gas mitigation interventions for health-care systems
13,14Box 2. Search strategy, 1: (netzero or net zero).mp.2: carbon footprint/ 3: greenhouse effect/ 4: exp climate change/ 5: (carbon or CO2 or methane or CH4 or nitrous oxide or N2O or hydrofluorocarbon* or HFC* or perfluorocarbon* or PFC* or F-gas or fluorinated gas or sulfur hexafluoride or SF6 or nitrogen trifluoride or NF3 or emission* or greenhouse or GHG or climate change* or global warming or footprint or eco-friendly or climate friendly or environment* friendly or eco-efficient or environment* responsible or environment* sound or energy-efficient or energy-saving or green initiative* or environmental impact or short-lived climate pollutant or black carbon).mp.6: (environment* and sustainable*).mp.7: 1 or 2 or 3 or 4 or 5 or 6 8: exp "delivery of healthcare"/ 9: exp health facilities/ 10: (health system* or health care or healthcare or health sector or health supply chain* or health service* or delivery of health or health delivery or health facility* or health cent* or hospital or hospitals or clinic or clinics or emergency department* or operating* room* or operating* theatre* or patient care or ward* or urgent care or primary care or secondary care or tertiary care or quaternary care or telemedicine or medical cent* or diagnostic care or rehabilitative care or preventative care or palliative care or home care).mp.Bull World Health Organ 2024;102:159-175B| doi: http://dx.doi.org/10.2471/BLT.23.290464Iris Martine Blom et al.Greenhouse gas mitigation interventions for health-care systems

Table 1 . Detailed summary of included studies on greenhouse gas mitigation interventions for health-care systems Study Study design Year of intervention Country, WHO region Income level Health system level Study site(s)
44: not reported; WHO: World Health Organization.Note: Income level follows the classification of the World Bank.44BullWorld Health Organ 2024;102:159-175B| doi: http://dx.doi.org/10.2471/BLT.23.290464Iris Martine Blom et al.Greenhouse gas mitigation interventions for health-care systems

Table 5 . Certainty of evidence for interventions to mitigate greenhouse gases for health-care systems, low-and middle-income countries
2 : carbon dioxide; RCT: randomized controlled trial.aWe used the Grading of Recommendations Assessment, Development, and Evaluation approach.bResults (partially) based on visual observation of pollution.cOutcomes in electricity generated in carbon dioxide equivalent using national emission factors.dAdaptation was a consideration in the article and not measured.Bull World Health Organ 2024;102:159-175B| doi: http://dx.doi.org/10.2471/BLT.23.290464IrisMartine Blom et al.©

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